The Background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present disclosure.
Radio frequency receivers can convert a received radio frequency signal to a lower intermediate frequency (fIF) prior to demodulating the received signal. The lower fIF simplifies the design of bandpass filters (BPFs) that are used to separate a wanted or selected channel from adjacent channels. For example, analog broadcast FM receivers receive selected channels centered between 88 MHz and 108 MHz and use an IF value of 10.7 MHz. Such relatively high IF frequency can cause the receiver to be too complex and often requires a high quality-factor discrete BPF to remove unwanted adjacent channel energy. To reduce this complexity and cost, and to reduce the size of the circuitry and increase system integration, some applications use a much lower fIF (100-200 kHz) that is compatible with an integrated BPF. An example of such an application includes GSM cellular phones. However reducing fIF increases the difficulty of filtering a DC offset and/or 1/f noise from the received signal.